Balance roller for lever escapement of a timepiece



Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE Filed Dec. 29, 1955 4Sheets-Sheet 1 PRtOR ART INVENTOR Paul Tuareg ATTORNEY Dec. 16, 1958 P.TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE- Filed Dec. 29, 1955v 4 Sheets-Sheet 2 INVENTOR ATTO R N EY Dec. 16, 1958 P. TUETEY2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE Filed Dec. 29, 1955 4Sheets-Sheet 5 Paul Tuer mm ATTORN EY Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE.

Filed Dec. 29, 1955 4 Sheets-Sheet 4 H613 r p -15 Y 1w a INVENTOR. PaulTuereg United States Patent BALANCE ROLLER FOR LEVER ESCAPEMENT OF ATIMEPIECE Paul Tuetey, Le Locle, Switzerland, assignor to Les FabriquesdAssortiments Runies, Le Locle, Switzerland Application December 29,1955, Serial N 0. 556,241 Claims priority, application SwitzerlandFebruary 25, 1955 9 Claims. (Cl. 58121) The present invention relates toa lever escapement of timepieces and more particularly to a balanceroller for lever escapement and to a process of manufacture of same.

Up to now the impulse pin or roller jewel adapted to cooperate with thepallet fork or lever was driven in or maintained by means of gum-lac ina bore stamped out in the roller.

Fixing a pin by driving it into a suitable bore of the rollernecessitates a very high precision of these elements. The impulsepinshould have bevelled edges so as to penetrate more easily into thebore and to avoid and additional stamping out of said bore. On the otherhand, according to the material used for making the impulse pin(synthetic jewels), which is more or less fragile, there often occurgrinding or breaking of the pin, resulting in the loss of the rollersince it is practically impossible to replace a broken pin.

Securing the impulse pin by means of gum-lac necessitates a bore in theroller, the dimensions of which are somewhat larger than those of thepin. The latter may, therefore, assume different positions and the mostfrequent drawback is the lack of perpendicularity of the pin axis withrespect to the plane of the roller. In addition, the gum-lac runs overon the roller and at the moment of assembling the roll onto the balancestaff, it comes sometimes into contact with a flange of said staff,resulting in breaking the gum-lac and causing the pin to fall. Finally,the gum-lac is often dissolved by the liquids used for cleaning thebalances.

The invention aims at overcoming the above-mentioned drawbacks. To thisend, the balance roller carrying an impulse pin comprises a central dischaving a non-circular recess receiving the pin, said pin being securedin its position by means of a ring bearing both on the pin and on theperiphery of the disc.

The balance roller is generally rigidly fixed to a small roller adaptedto cooperate with the guard pin or dart of the pallet fork or lever. Upto now, the bore of the large roller adapted to receive the impulse pinand the notch of the small roller had to be executed separately with therisks of imprecision involved therewith. As a matter of fact, the radialalignment of the pin bore and of the notch was not guaranteed, so thatthe safety functions of the escapement were not made correctly.

, 2,864,232 Patented Dec. 16, 19 53 Fig. 3 is an elevation view of thelever escapement shown in Fig. 2.

Fig. 4 is a perspective exploded view of the same embodiment at anenlarged scale.

Fig. 5 is a perspective view corresponding to Fig. 4, but in which theparts of the roller are assembled to one another.

Figs. 6 to 11 are bottom views of six other embodiments, at a reducedscale.

Figs. 12 and 13 are cross-sectional views of two modified structures.

Referring to Fig. 1, it will be seen the end portion of a lever orpallet fork 1 and a double balance roller 2, 3 of a lever escapement ofa known construction. The limiting pins of the lever 1 are denoted bythe numerals 4, the impulse pin or roller jewel by 5, the notch of thesmall roller by 6, the horns of the lever by 7, the guard pin or dart by8, the balance staff by 9 and the roller can non by 10.

The construction illustrated in Figs. 2 and 3 difiers from that of Fig.1 especially in the manner in which the impulse pin 5 is secured to thelarge roller and in the greater radius of the small roller.

The large roller comprises a central disc 11 having a non-circularrecess 12 obtained for instance by a milling operation. The recess 12 ismachined in such a way that the pin 5, when put into position, slightlylies outside the circumference of the disc 11. As usually, the pin 5 hasan approximately semicylindrical shape and it is its plane face whichcloses the open side of the recess 12. A ring 13, which is driven ontothe disc 11, holds the pin 5 in position. w

This assembling system of the impulse pin and ofthe large roller permitsmachining simultaneously the recess 12 and the notch 14 of the smallroller '15. This machining is made in a single operation and with thesame tool, preferably by milling. Thus, the notch 14 of the small rollerhas the same shape as a portion of the recess 12 of the large roller andis situated in the axial prolongation of thisportion. The risksofimpr'ecisio'n mentioned above are therefore done away with, as theradial alignment of the place receiving the pin and of the notch of thesmall roller is now guaranteed. The safety functions of the escapementare made correctly; any subsequent checking is superfluous and animportant cause of refuse in the manufacture is removed.

Another advantage of the described construction consists in thepossibility of giving to the roller cannon a larger radius, so that theradius of the roller hole 19, whose machining is always difiicult, canbe increased or else the strength of the roller can be reinforced by in-The invention also permits overcoming this difiiculty as it relates inaddition to a process of manufacture of the double roller (large rollerand small roller), in which the recess of the large roller adapted toreceive the impulse pin and the notch of the small roller are machinedFig. 1 shows for comparison purposes a bottom view of a portion of alever escapement of a known construction.

Fig. 2 is a view corresponding to Fig. 1 of the first embodiment of theinvention and of the lever co-operating therewith.

creasing the thickness of the cannon wall. As a matter of fact, it willbe seen in Fig. 1 that the'ends of the horns 7 do not permit giving tothe cannon 10 'a radius r guaran teeing' a sufficiently thick Wall. Onthe contrary, in the escapement shown in Fig, 2, the ends of the horns16 have been appreciably shortened, so that the radius r of the cannon17 can be made somewhat greater. It was possible to shorten the horns 16owning to the increase of the radius R of the small roller 3 .(Fig. 1),which becomes R for the small roller 15 of Fig. 2, and owing to thedecrease of the angular width of the notch of' the smallroller, whichpasses from the value a (Fig. 1 to the value a, (Fig. 2).

At firstsight, it might seem that the possibility of increasing theradius of the roller cannon does not depend on the invention. Inreality, the radius of the cannon only depends on 'the'length of thehorns 7 or 16 respectively ofthe lever 1. This length in turn isconditioned .by the necessity of avoiding any overbanking of the lever 1between the moment when thedar't- 8 or- '18 respectively is no longer incontact with the small roller 3 or '15 respectively (Within the range ofthe notch) and the moment when the pin 5 enters the opening of thelever. This lapse of time is the shorter as the radius of the smallroller is greater or the dart is wider. In the construction illustratedin Fig. 2, machining of the notch 14 of the small roller 15 with thesame tool as for the recess 12 makes it necessary to shorten the dart 18and therefore to increase the radius of the small roller .15. It resultsnaturally therefrom that, since the length of the horns 16 may bereduced, the radius of the cannon 17 may be increased.

The shape of the recess 12 and of the notch 14, instead of beingsemicylindrical as in Figs. 2 to 5, may be modified in order tofacilitatethe machining by means of milling tools having a profile easyto draw up. Thus, in the embodiments shown in Figs. .6 and 9 to 11, therecess 12a and the notch14a have a rectangular cross-section, Whereas inthe embodiment of Fig. 7 they have the shapeof a slightly obtusedihedral angle and are denoted by 12b and 14b, respectively. In theexample of Fig. 8 the cross-section of the recess 12c and of the notch140 is trapezoidal.

It is not indispensable that the ring 13 be driven onto the disc 11. Itsputting in place might be done by means of a preliminary elasticdeformation which would be rendered possible by a suitable shape of thedisc 11 which would have only a limited number .of points of contactwith the ring 13, as illustrated in Figs. 8 and 9 in which the discs aredenoted by 110 and 11a, respectively.

It is also not necessary that the impulse pin 5 lie partially outsidethe circumference of the disc 11. It is possible to hold it in positionalso in such a case. Figs. 10 and 11 show two constructions with thisfeature, the rings being denoted by.13a and 13b, respectively.

The large roller and the small roller are generally made integral witheach other. However, the two-piece construction was also executedpreviously and in certain cases the small roller was made integral withthe balance staff. Up to now nobody has succeeded in making the doubleroller integral with the balance staff, as it was necessary to stamp outin the large roller the bore adapted to receive the impulse pin. On thecontrary, owing to the above-mentioned machining of the open recess 12,it is now possible to make in one piece the disc 11, the small roller 15and the balance staff 9 (Fig. 13). In a modified structure, the disc 11is made integral only with the balance staff 9, whereas the small roller15 is held by a drive fit on the balance statf 9 (Fig. 12).

While the invention has been described and illustrated with reference tospecific embodiments thereof, it will be understood that otherembodiments may be resorted to without departing from the invention.Therefore, the form of the invention set out above should be consideredas illustrative and not as limiting the scope of the follow? ing claims.

I claim:

1. A balance-roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc of uniform thickness having at its periphery a non-circularrecess, open towards the outside and rec-eiving the impulse pin, and anouter ring surrounding the central disc and hearing both on the pin andon the periphery of the disc so as to press the pin against the wall ofthe recess and thus secure the pin in its position.

2. A :balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc of uniform thickness having at its periphery a non-circularrecess, open towards the outside and receiving the impulse pin, the pinlying partially outside the circumference of the disc, and an outer ringsurrounding the central disc and bearing both on the pin and on theperiphery of the disc so as to press the pin against the wall of therecess and thus secure the pin in its position.

3. A balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc of uniform thickness having at its periphery asemicylindrical recess open towards the outside and receiving theimpulse pin, and an outer ring surrounding the central disc and bearingboth on the pin and on the periphery of the disc so as to press the pinagainst the wall of the recess and thus secure the pin in its position.

4. A balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc having a non-circular recess receiving the impulse pin, andan outer ring surrounding the central disc and bearing both on the pinand on the periphery of the disc so as to press the pin against the Wallof the recess and thus secure the pin in its position, the ring beingheld by a drive fit.

5. A balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc having a. non-circular recess receiving the impulse pin,and an outer ring surrounding the central disc and bearing both on thepin and on the periphery of the disc so as to press the pin against thewall of the recess and thus secure the pin in its position, the ringbeing held in position by elastic deformation.

6. A balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc having a non-circular recess receiving the impulse pin, andan outer ring surrounding the central disc and bearing both on the pinand on the periphery of the disc so as to press the pin against the wallof the recess and thus secure the pin in its position, the impulse pinbeing placed within the circumference of the disc.

7. A balance roller for lever escapement of a timepiece, carrying animpulse pin adapted to cooperate with the lever, the roller comprising acentral disc having a non-circular recess receiving the impulse pin, andan outer ring surrounding the central disc and bearing both on the pinand on the periphery of the disc so as to press the pin against the wallof the recess and thus secure the pin in its position, the disc beingmade integral with the balance staff.

8. A balance roller assembly for lever escapement having a lever with aguard pin of a timepiece, carrying an impulse pin adapted to cooperatewith the lever, the roller assembly comprising a central disc having anoncircular recess receiving the impulse pin, and an outer ringsurrounding the central disc and bearing both on the pin and on theperiphery of the disc so as to press the pin against the wall of therecess and thus secure the pin in its position, a small roller, the discbeing rigidly fixed to the small roller which is adapted to cooperatewith the guard pin of the lever, the central disc and the small rollerbeing made integral with the balance staff.

9. A balance roller assembly for lever escapement having a lever with aguard pin of a timepiece, carrying an impulse pin adapted to cooperatewith the lever, the roller assembly comprising a central disc having anoncircular recess receiving the impulse pin, and an outer ringsurrounding the central disc and bearing both on the pin and on theperiphery of the disc so as to press the pin against the wall of therecess and thus secure the pin in its position, a small roller, the discbeing rigidly fixed to the small roller which is adapted to cooperatewith the guard pin of the lever, the notch of the small roller havingthe same shape as a portion of the recess of the disc and being situatedin the axial prolongation of said portion.

References Cited in the file of this patent UNITED STATES PATENTS

